i got my new 460 together and it has roughly 40 miles on it and roughly 2 hours worth of idle time. i was driving all of a sudden and its backfiring thru the carb pretty bad. its funny how it didn't do it until 40 miles and 2 hour of idling.

i'm about 5k elevation and the stock timing is roughly 12 i believe cuz its says so on my valve covers. the absolute lowest i can put it without running really rough is about 20btc. my neighbor thought i was off a tooth and he said a cheap easy wya to fix that is pull vacuum dia out more and push the wires out 1 wires the other direction. my vacuum dia was a little close on the driver side.

after that i could get it to run decent at 16btc. but before i did this it started popping and it would do it right away. after i did this when the timing is at 16btc, it would do it at idle only a bit, but only once in a blue moon during accel. i went out driving for roughly 2 miles and it didn't do it so i went back home ot get a drink of water. went back out and it backfired driving away from my house. drove another mile down the neighborhood and it backfired and died. once i got on my street it backfired right a few times then died right infront of my house and kept on backfiring and dying until i got her into the garage a few times.

do you think i'm entirely off on timing? i got good cap and rotor, my wires are still brand new and are ford racing ones. maybe valve adjustment?

any help and fast help would be appreciated.

 

Timing and/or vacuum off.
Whatever you did (per neighbor's suggestion) put it back and deal with any timing issue directly.
Get it running decently at operating temps, set up vacuum guage at intake manifold. Don't look at timing marks, set timing by highest guage reading.
Then tinker with timing marks if need be.

Is engine/intake all stock?

 

no the motor is in a 71 mustang so its definetly not going to be stock in my taste. however i got a 274 286 dur cam with 562 564 lift cam. its a extreme energy series from comp and the cam is listed as a street machine cam. the intake is a offenhauser port o sonic intake with a 870 carb street avenger.

so regardless what my timing mark is showing, it could be off and just go by vacuum?

however when i stabed the dist, i think i remember reading for the motor to start up right away and not needing to play with the dist is to have the timing mark at 10btc when the number 1 cylinder is pointing at #1 cylinder. so i did that. if that isn't right maybe thats why i'm off on timing. but also, i can advance the timing so much it will die.

how will a vacuum cause carb backfire? i could check if i have a vacuum leak but my brakes work fine and my transmission shifts.

 

Recheck the firing order of the plug wires before you do anything. If the backfire showed up when you moved them, I suspect at least 2 of them got switched.

 

it backfired before too so i don't think this is the cae. but i did check to see if the firing order is right and it is.

 

You need to know what the timing is in the distributor?????

 

if you want, you can give it to me just in case i'm wrong.

 

Excellent, thank you.

 

i tried that this time but its popping as soon as you start it and it backfires itself off. i'm going back to the TDC drawing board later today.

 

Check TDC, firing order and fully seated distributor

 

You need to look through a window in the distributor plate rotate the distributor untill you see the slot in the plate with the tab in it and read the numbers stamped in the plate 2 x that number is you distributor total timing subtract that from around 36 to get your inital timing. Plates have 2 positions on slot might be a 18 and the other a 15 or a 15 and a 10.


Plate stamped 13 X 2= 26 ..... 36-26 = 10 <--- your inital timing.

I modify my plates and run about 6 to 8 in the distributor total 12 to 16 and inital from 18 to 22 depending on reading spark plugs.

 

well i was going to try to get TDC right on tonight so i took off the valve covers and etc and i found rocker 5E loose. loose enough to where i can lift up on it a bit and get the pushrod off of the rocker. i crank over the motor and i watch all the other E rockers and i see them go down a nice bit, but this 5E rocker isn't going down as much as the others.

so i'm thinking just after 40 miles i got a wiped out lobe. and i just got the motor running less than 30 days ago. thank god i got the warranty on the motor still from the machine shop. they better replace the cam and lifters for free and do all the labor that is required to replace the cam after a wiped lobe.

what i'm maybe somehow hoping for is maybe a lifter has collasped and is stuck in a down position. this is what i'm hoping for. pray for me guys.

 

is the pushrod bent???? yank it out and roll it on a glass table to see if it is striaght??? if its bent i would check the rest...

 

i check for that and it doesn't appear to be bent at all but i'll make sure. i also checked to see if maybe the plunger is shot and it isn't because its very hard to pushdown on it and its like a rock (i've had a bad one where you can pushdown on it with the pushrod)


the machine shop better replace the cam for free. and it'll be nice if they will replace it with a roller cam so there is no chance of a lobe flattening and i'm sure i'll pay for the difference.

if the pushrod ain't bent, lifter is solid, its got to be the cam flattened a bit.

i'm assuming that is the reason for my carb backfiring.

 

yup, pushrod is not bent. bad news for me huh? and i thought i heard the machinist i went to say that a cam lobe should wipe out very soon after initial start up or shorterly after a few miles.